Safety first! Electronics is a potentially dangerous hobby. Any circuit that works with 120 VAC power from an electrical outlet is especially dangerous and could potentially kill you. Here are some safety guidelines to keep you safe as you work:
Never work on a circuit while power is applied.
Do not connect power to a circuit until the circuit is finished and you have carefully checked your work.
If you smell anything burning, immediately disconnect the power and examine your circuit to find out what went wrong.
Keep your work area dry.
Always wear safety goggles.
Be careful around large capacitors; they can continue to hold voltage long after they are disconnected from power.
Be especially careful when you solder because a hot soldering iron can easily burn you.
Always work in a well-ventilated space.
Have safety equipment such as a fire extinguisher, a first-aid kit, and a phone nearby.